- Hardwood chips or shreds
- Bark chips or shreds
- Leaves
- Pecan shells
- Straw
- Pine needles
By Gail Dugelby. Mulch is a vital component of a successful garden and landscape. When applied correctly, there are significant pros to using it to help your plants and trees.
What exactly is mulch, should you use it and how do you use it? You’ve likely pondered these and many other questions about mulch. Stick with me as I break down the benefits of this mysterious material. Mulch is a layer of material applied to the surface of the soil, especially in landscape beds. Properly used, it can help plants retain moisture and enhance the quality of the soil. While we most often see mulch as wood chips, there are both organic and inorganic options.
Let’s start with types of mulches. Here are some examples of organic mulch:
Organic mulches
How to know which one is right for you is a personal choice, but there are more pros to organic mulch.
- Increases water-holding capacity and retains moisture in soils.
- Adds carbon (the energy food) to the soil.
- Assists plants with drought tolerance and nutrient absorption.
- ncourages root growth.
- Reduces soil temperature.
- Inhibits weed germination and growth.
- Provides soil structure that allows air and water to penetrate.
- Encourages beneficial soil organisms like bacteria, fungi and earthworms.
- Increases macro and micro-organism interaction.
- Reduces plant competition (cover).
Additionally, there is a type on the market called “living mulch.” It combines mulch (usually hardwood chips) with a good compost mix. This adds a good amount of nutrients to the soil in addition to the benefits of organic mulch.
In the past, people have used “inorganic” mulches such as rocks, decomposed granite or rubber chips. Just don’t. Inorganic mulches seldom provide any nutritional benefit and increase urban heat, flooding, and maintenance. Other types like decomposed and rolled granite are added to the landscape with the assumption they facilitate drainage for xeric plants or reduce maintenance. They can increase maintenance by running off in heavy rains and can cause sprouting of fallen seeds from trees and bird droppings.
We strongly advise applications of organic mulch in spring and fall to achieve maximum benefits, so now is a great time for a mulch application.
How to mulch? Even very small amounts, one inch or so, of woodchips, leaves or pecan shells significantly reduces soil temperatures. It’s preferable to maintain between 1-2 inches of mulch on your garden beds.
How about no mulch at all?
Examples of when you don’t have to mulch is if you’re creating a truly native landscape, like a wildflower meadow or pocket prairie. These types of landscapes cover almost every bit of soil with plant material and leave little to no room for mulch.
One last word about mulch around trees. Trees ‘breathe’ around the base of their trunk, the area called the root flare. (It’s where the trunk meets the ground flaring out from the tree.) Never pile up mulch next to, on top of, or over the root flare. Limited oxygen in the soil and excessive moisture on roots around the trunk provide excellent conditions for fungi, bacteria and insects to do their dirty deeds.
If Mother Nature doesn’t do it, neither should you. Piling up mounds of mulch against tree trunks is harmful. Rule of thumb: no more than two inches of mulch in depth around the tree and never within two to three inches of the trunk.
Mulch is a vital component of a successful garden and landscape. When applied correctly, there are significant pros to using it to help your plants and trees.
Gail Dugelby is a SAWS conservation consultant with deep roots in San Antonio and the Hill Country. She spent her youth climbing trees, playing in the Guadalupe River, and exploring the outdoors. This drives her passion for nature and our diverse environment, especially our most precious natural resource — water. Given the choice, she would be outside all the time.